I don't know what crazy rules the USA has in place now, but it is normal for people to change their hair style and colour. The purpose of the passport photo is to assure the border agent that the person offering the passport as identification is indeed the person it was issued to. So it is important that it resembles your normal appearance. That is what the guidelines for Canadian passport photos say: that it must look like your normal appearance.
When I went for my passport photo, I just kept my wig on. No one asked me to take it off, and I didn't offer to. It was my "everyday" wig, so it is how I would normally look boarding a plane. They did ask me to adjust my bangs and the hair over my ears, because eyebrows and ears must be visible. I just did a hand-comb in front of the mirror until the photographer was satisfied that I met the requirements. I got my passport, so I must have done it right.